1. Field of the Invention
The present invention relates to an image sensor used for an image inputting unit of an image inputting device.
2. Description of Related Art
FIG. 8 is a cross-sectional view showing the configuration of an image sensor disclosed in Published Unexamined Japanese Patent Application No. H4-111664 (1992) as a first prior art. FIG. 9 is a side view seen from the F direction in FIG. 8. In FIG. 8 and FIG. 9, 101 indicates an image sensor, 102 indicates a glass plate placed along a manuscript running plane, and 103 indicates a sensor frame. 104 indicates a line light source composed of a plurality of light emitting diodes (LED) arranged in a line. A surface of a manuscript 113 running on the glass plate 102 is illuminated with light emitted from the line light source 104. 105 indicates a holding member which is fixed on the sensor frame 103 and holds the line light source 104. 106 indicates a rod lens array composed of a plurality of rod lenses arranged in a line. A plurality of rays of light reflected on the surface of the manuscript 113 are converged by the rod lens array 106 to form an erecting image at equal magnification. 107 indicates a long groove formed in the sensor frame 103, and the rod lens array 106 is arranged in the long groove 107. 108 indicates a long hole formed in the sensor frame 103, and the light emitted from the rod lens array 106 passes through the long hole 108. 109 indicates each of a plurality of screws for fixing the rod lens array 106 to the sensor frame 103. 110 indicates a sensor integrated circuit (IC) composed of a plurality of light receiving devices arranged in a line. The rays of light, which are reflected on the surface of the manuscript 113 and pass through the rod lens array 106, are received in the sensor IC 110. 111 indicates a sensor substrate on which the sensor IC 110 is mounted. 112 indicates each of a pair of side plates arranged on both ends of the sensor frame 103 in a longitudinal direction of the rod lens array 106 (or a direction perpendicular to a plane shown in FIG. 8).
Also, FIG. 10 is a cross-sectional view showing the configuration of another image sensor disclosed in the Published Unexamined Japanese Patent Application No. H4-111664 (1992) as a second prior art. FIG. 11 is a side view seen from the G direction in FIG. 10. In FIG. 10 and FIG. 11, 121 indicates an image sensor. 122 indicates each of a pair of springs attached to the side plates 112 respectively. The springs 122 push both end portions of the rod lens array 106. 123 indicates each of a pair of screws for pushing the rod lens array 106 toward the springs 122 to fix the rod lens array 106 between the springs 122 and the screws 123. The other constituent elements, which are equivalent to or the same as those shown in FIG. 8 or FIG. 9, are indicated by the same reference numerals as those of the constituent elements shown in FIG. 8 or FIG. 9, and additional description of those constituent elements is omitted.
The focus adjustment performed in the image sensors 101 and 121 is described with reference to FIG. 12.
FIG. 12 is a view showing an operation of the rod lens array 106. As shown in FIG. 12, rays of light reflected on the surface of the manuscript 113 at a point P pass through the rod lens array 106 and are converged at a point Q to form an image. Here, an optical distance X from the point P to the center of the rod lens array 106 is equal to an optical distance Y from the center of the rod lens array 106 to the point Q. Therefore, in the assembly operation of each of the image sensors 101 and 121, the position of the rod lens array 106 is adjusted so as to place the sensor IC 110 at an image forming position at which the rays of light reflected on the surface of the manuscript 113 is converged. Therefore, the image sensor is brought into focus.
In detail, in the first prior art, the rod lens array 106 is moved up and down as shown by double-headed arrows in FIG. 9. Thereafter, when the sensor IC 110 is placed at an image forming position at which the rays of light reflected on the surface of the manuscript 113 are converged, the rod lens array 106 is pushed on a wall of the sensor frame 103 opposite to the screws 109 so as to fix the position of the rod lens array 106. Therefore, the image sensor 101 is adjusted so as to place the sensor IC 110 at the image forming position at which the rays of light reflected on the surface of the manuscript 113 are converged.
Also, in the second prior art, the rod lens array 106 receives a resilient force of the springs 122. Therefore, when the screws 123 are driven, the rod lens array 106 is moved up as shown by double-headed arrows in FIG. 11. In contrast, when the screws 123 are loosened, the rod lens array 106 is moved down as shown by double-headed arrows in FIG. 11. Therefore, when the sensor IC 110 is placed at an image forming position at which the rays of light reflected on the surface of the manuscript 113 are converged, the turning of the screws 123 is stopped. Therefore, the position of the rod lens array 106 is adjusted so as to place the sensor IC 110 at the image forming position at which the rays of light reflected on the surface of the manuscript 113 are converged.
Next an operation of each of the image sensors 101 and 121 is described.
When the manuscript 113 runs on the glass plate 102, the surface of the manuscript 113 is illuminated with rays of light emitted from the line light source 104 through the glass plate 102. The rays of light are reflected on the surface of the manuscript 113 and have intensities corresponding to light and shade conditions of an image drawn in the manuscript 113. The rays of light reflected on the surface of the manuscript 113 passes through the rod lens array 106 and the long hole 108 of the sensor frame 103 and are converged on the sensor IC 110 to form the image of the manuscript 113, and the reflected light is received in the sensor IC 110. Thereafter, a photoelectric conversion is performed in the sensor IC 110 for the light reflected on the surface of the manuscript 113 according to the intensities of the rays of reflected light, and light and shade information of the image drawn in the manuscript 113 is output to the outside through the sensor substrate 111.
Because the image sensor 101 of the first prior art has the above configuration, there are following problems.
FIG. 13 is a top view of the image sensor 101 and shows the long groove 107 and the long hole 108 in a screw driving condition. FIG. 14 is an enlarged top view of an end of the long hole 108 shown in FIG. 13.
As shown in FIG. 13, when the screws 109 are driven, the long groove 107 and the long hole 108 are widened, and an opening is generated between the sensor frame 103 and the rod lens array 106. As shown in FIG. 14, the long hole 108 of the sensor frame 103 does not reach any side plate 112 placed on both sides of the sensor frame 103 but is surrounded by the sensor frame 103 at both ends of the long hole 108. Therefore, an area of the opening at the center of the long groove 107 and the long hole 108 is wider than that at both ends of the long groove 107 and the long hole 108. Therefore, light leaks through the opening between the sensor frame 103 and the rod lens array 106, and the leaking light overlaps with the light which is reflected on the manuscript 113 and is converged by the rod lens array 106 on the sensor IC 110. As a result, a problem has arisen that the light and shade information indicating the image drawn in the manuscript 113 cannot be correctly obtained in the image sensor 101.
Also, when the screws 109 are driven, the top portions of the screws 109 are rotated on the surface of the rod lens array 106. Therefore, a surface portion of the rod lens array 106 is scraped by the screws 109 and results in the generation of foreign particulate matter. This foreign particulate matter passes through the opening between the sensor frame 103 and the rod lens array 106 and lay thick on the sensor IC 110. Therefore, another problem has arisen that the foreign particulate matter prevents the light and shade information indicating the image drawn in the manuscript 113 from being received in the sensor IC 110.
Also, when the screws 109 are driven, the long groove 107 and the long hole 108 are widened, and an external shape of the sensor frame 103 is deformed. As shown in FIG. 13, a width I at the center of the sensor frame 103 becomes longer than a width H at each end of the sensor frame 103. The difference between the widths I and H depends on a clamping torque of the screws 109. Therefore, another problem has arisen that it is difficult to design shapes for parts which are disposed adjacent to the image sensor 101.
Also, in the second prior art, because the image sensor 121 has the above configuration, only each end of of the rod lens array 106 is fixed by the springs 122 and the screws 123. Therefore, in cases where the image sensor 121 which is lengthen in the longitudinal direction is used, a rod lens array 106 with corresponding lengthening in the longitudinal direction is used. Therefore, a considerable warp results in the rod lens array 106 due to the weight of the rod lens array 106 with the result that the rod lens array 106 is finally bent. In this case, a problem has arisen that the position of the rod lens array 106 cannot be adjusted so as to correctly place all the light receiving devices of the sensor IC 110 at the image forming positions of the light reflected on the manuscript 113 along the whole extending range of the rod lens array 106. In other words, a problem has arisen that the image sensor 121 cannot be focused on the manuscript 113 along the whole rod lens array 106 in the longitudinal direction.
Also, because the rod lens array 106 is lengthened in the longitudinal direction when both ends of the rod lens array 106 are fixed by the springs 122 and the screws 123, when an ambient temperature changes, the rod lens array 106 is bent due to the difference in coefficient of linear thermal expansion between the sensor frame 103 and the rod lens array 106. Therefore, another problem has arisen that the sensor IC 110 is placed out of the image forming position at which the light reflected on the manuscript 113 is converged. In other words, another problem has arisen that the image sensor 121 cannot be focused on the manuscript 113.
A main object of the present invention is to provide, with due consideration to the drawbacks of the conventional image sensor, an image sensor in which light and shade information of an image drawn in a manuscript is correctly obtained.
Also, a first subordinate object of the present invention is to provide an image sensor in which the reception of light and shade information of an image drawn in a manuscript is not prevented.
Also, a second subordinate object of the present invention is to provide an image sensor in which an external shape of a frame is not deformed.
Also, a third subordinate object of the present invention is to provide an image sensor which is focused on a manuscript in a whole extending range of a rod lens array along a longitudinal direction.
Also, a fourth subordinate object of the present invention is to provide an image sensor which is focused on a manuscript regardless of the change of an ambient temperature.
The main object is achieved by the provision of an image sensor comprising a light source for illuminating a surface of a manuscript, a rod lens array for converging rays of light reflected on the surface of the manuscript, a light receiving element for receiving the rays of light converged by the rod lens array, a frame for fixing the rod lens array, and a holding and adjusting element for holding the light receiving element, adjusting a distance between the rod lens array and the light receiving element to arrange the light receiving element at an image forming position at which the rays of reflected light are converged so as to form an image drawn in the manuscript.
In the above configuration, the position of the rod lens array is fixed by the frame before the adjustment of the distance between the rod lens array and the light receiving element in the assembling of the image sensor. Thereafter, a position of the light receiving element is adjusted by the holding and adjusting element so as to arrange the light receiving element at the image forming position. That is, a positional adjustment of the rod lens array is not performed, but a positional adjustment of the light receiving element is performed. Because the light receiving element is merely held by the holding and adjusting element, no external force is given to the light receiving element in the assembling and adjusting of the image sensor. Accordingly, the distance between the rod lens array and the light receiving element can be correctly adjusted, and light and shade information of the image drawn in the manuscript can be correctly obtained in the image sensor.
It is preferred that the frame has both a first frame portion and a second frame portion separated from each other, and the rod lens array has a plane of incidence, a light emitting plane opposite to the plane of incident plane, a first side surface extending in parallel to a longitudinal direction and a second side surface opposite to the first side surface and is arranged between the first and second frame portions of the frame so as to make the first frame portion of the frame tightly come into contact with the first side surface of the rod lens array and so as to make the second frame portion of the frame tightly come into contact with the second side surface of the rod lens array.
In the above configuration, the first frame portion of the frame tightly comes into contact with the first side surface of the rod lens array, and the second frame portion of the frame tightly comes into contact with the second side surface of the rod lens array. In this case, no light leaks through a contacting area between the first frame portion of the frame and the first side surface of the rod lens array, and no light leaks through a contacting area between the second frame portion of the frame and the second side surface of the rod lens array. Therefore, light passing through the outside of the rod lens array does not reach the light receiving element. Also, no foreign matter passes through a contacting area between the first frame portion of the frame and the first side surface of the rod lens array, and no foreign matter passes through a contacting area between the second frame portion of the frame and the second side surface of the rod lens array. Therefore, no foreign matter is put on the light receiving element.
Accordingly, the reception of light and shade information of the image drawn in the manuscript is not prevented in the image sensor.
It is preferred that the frame has a long hole through which the rays of light emitted from the rod lens array pass, and the rod lens array tightly makes contact with a plane of the sensor frame adjacent to a side of the long hole so as to cover the side of the long hole with the rod lens array.
In the above configuration, no light leaks through a contacting area between the rod lens array and the plane of the sensor frame, and no foreign matter passes through a contacting area between the rod lens array and the plane of the sensor frame. Therefore, light passing through the outside of the rod lens array does not reach the light receiving element, and no foreign matter is put on the light receiving element.
Accordingly, the reception of light and shade information of the image drawn in the manuscript is not prevented in the image sensor.
It is preferred that the holding and adjusting element comprises a plate-shaped member having a plate-shaped holding member for holding the light receiving element, and a plate-shaped adjusting member, which is connected with the plate-shaped holding member and makes contact with an end surface of the frame, for adjusting the position of the plate-shaped holding member by moving on the end surface of the frame, and a fixing member for fixing the plate-shaped adjusting member on the end surface of the frame at a plurality of fixing positions after the plate-shaped adjusting member is moved on the end surface of the frame to adjust the distance between the rod lens array and the light receiving element and to arrange the light receiving element at the image forming position.
In the above configuration, the position of the plate-shaped holding member is adjusted by moving the plate-shaped adjusting member on the end surface of the frame, and the plate-shaped adjusting member is fixed on the end surface of the frame at a plurality of fixing positions.
Accordingly, the position of the light receiving element can be easily adjusted in the image sensor. Also, an external shape of the frame is not deformed, and shapes for parts which are disposed adjacent to the image sensor can be easily designed in the image sensor.
It is preferred that the plate-shaped adjusting member is fixed on the end surface of the frame at three fixing positions or more by the fixing member.
Accordingly, the distance between the rod lens array and the light receiving element can be correctly adjusted in the whole extending range of the rod lens array along a longitudinal direction. Also, even though an ambient temperature changes, the position of the light receiving element placed at the image forming position, at which the light reflected on the surface of the manuscript is converged, can be reliably maintained.
It is preferred that an image sensor further comprises a sealing member, arranged between the plate-shaped holding member and the frame, to seal a passage extending from an outside of the image sensor to the light receiving element.
Accordingly, the sealing member can prevent foreign particulate matter of the outside from coming into the image sensor.
It is preferred that the holding and adjusting element comprises a plate-shaped holding member for holding the light receiving element, an adjusting member for supporting the plate-shaped holding member at a plurality of supporting positions and adjusting the distance between the plate-shaped holding member and the frame so as to arrange the light receiving element at the image forming position, and an elastic member, arranged between the plate-shaped holding member and the frame, for giving a resilient force to the plate-shaped holding member and the frame to make the plate-shaped holding member be apart from the frame.
Accordingly, the position of the light receiving element can be easily adjusted in the image sensor. Also, an external shape of the frame is not deformed, and shapes for parts which are disposed adjacent to the image sensor can be easily designed in the image sensor.
It is preferred that the plate-shaped holding member is supported by the adjusting member at three supporting positions or more.
Accordingly, the distance between the rod lens array and the light receiving element can be correctly adjusted in the whole extending range of the rod lens array along a longitudinal direction. Also, even though an ambient temperature changes, the position of the light receiving element placed at the image forming position, at which the light reflected on the surface of the manuscript is converged, can be reliably maintained.
It is preferred that an image sensor further comprises a sealing member, arranged between the plate-shaped holding member and the frame, to seal a passage extending from an outside of the image sensor to the light receiving element.
Accordingly, the sealing member can prevent foreign particulate matter of the outside from coming into the image sensor.